The present invention relates to a bicycle brake device and more particularly, to a bicycle brake device that is supported by fastening pins extending from the front fork or the rear fork of a bicycle, and that is driven by a brake cable for allowing the brake shoes to be pressed against the rim of the corresponding bicycle wheel.
Cantilever brakes, because of their strong brake power, are almost universally used on bicycles designed for off-road riding such as mountain bikes and all-terrain bikes. A cantilever brake device includes a left and a right brake arms having one end pivotally mounted on the fork of the bicycle frame, and a brake cable connected to the other end of the brake arms for actuating the brake arms to rotate in a closing direction when a bicyclist actuates a brake lever to pull the brake cable. Consequently, the brake shoes or pads that are installed on the intermediate portion of the brake arms include the braking surfaces facing the side surfaces of the bicycle wheel rim. The braking surfaces of the brake shoes may be pressed against the rim to produce braking action.
Examples of patents related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5.655,630, is a bicycle brake device.
U.S. Pat. No. 5,636,716, is a bicycle brake device.
U.S. Pat. No. 5,495.920, is a braking force adjusting apparatus for a bicycle.
Within the last decade or so, cantilever brakes with elongate arms, sometimes referred to as xe2x80x9cv-shapedxe2x80x9d brakes, have appeared on the market. These long-armed cantilever brakes provide a leverage, also known as mechanical advantage, over the traditional cantilever brakes. Specifically, the longer arms on these brakes result in a decreased ratio between the amount of finger pressure that a biker needs to apply to the brake lever and the amount of pressure consequently applied by the brake shoes to the wheel rim. This increased leverage is particularly desirable for long biking trips and downhill riding.
In 1996, Shimano, one of the largest bicycle manufacturers, introduced a new version of the V-brake into the market. The new version of the V-brake is a long-armed cantilever brake with a four-bar link mechanism that comprises four rigid links arranged as a parallelogram. When a bicyclist actuates the brake lever, the linkage pivots simultaneously with the brake arm for moving the brake shoe in a line of action normal to the side surface of the bicycle wheel rim. The flatly hitting of the brake shoes onto the wheel rim maximizes the braking power, and eliminates uneven pad wear, and eliminates the need to reposition pads as they wear down.
However, the four-bar link mechanism includes four links and their associated pin joints that complicate the brake manufacture and maintenance and that increase the cost of the brake device. The links also allow for xe2x80x9cplayxe2x80x9d or jiggling between associated parts that bikers find particularly noticeable under heavy breaking conditions. Furthermore, the four-bar brake mechanism produces excessive squeal that has caused so many complaints that Shimano has had to produce a special kit designed to deal with the squeal. Also, this design requires a restoring force, like a spring, to return the brake assembly to the unengaged or non-braking position.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional brake devices.
The primary objective of the present invention is to provide a brake device including a simplified compliant member for actuating the brake shoes to hit the wheel rim flatly.
In accordance with one aspect of the invention, there is provided a brake device for a bicycle, the brake device comprising a pair of brake arms each including a lower portion pivotally coupled to the bicycle at a pivot axle and each including a middle portion and an upper portion, the brake arms being caused to rotate about the pivot axle when the upper ends of the brake arms are forced toward each other, a pair of frames pivotally secured to the middle portions of the brake arms respectively at a pivot shaft, a pair of brake shoes attached to the frames respectively for acting onto a wheel rim of the bicycle when the upper ends of the brake arms are forced toward each other, a pair of seats secured on the pivot axles respectively, and a pair of compliant members each including a first end secured to the frame and a second end secured to the seat. The frames are caused to rotate relative to the brake arm about the pivot shaft respectively and to move the brake shoes to engage with the wheel rim in a horizontal attitude when the brake arm is rotated about the pivot axle.
A tube is secured on the pivot axle and includes at least one projection extended radially outward therefrom, the seat includes at least one notch formed therein for receiving the at least one projection of the tube and for securing the tube and the seat together.
An adjusting device is further provided for adjusting the compliant member relative to the seat and to adjust the frame and the brake shoe to rotate about the pivot shaft. The seat includes a protrusion having a screw hole formed therein, the adjusting device includes a screw threaded in the screw hole of the seat and engaged with the compliant member for moving and adjusting the compliant member relative to the seat when the screw is threaded relative to the protrusion of the seat.
The frames each include an extension extended therefrom, and the seats each include a bulge formed thereon. The first ends of the compliant members are secured to the extensions of the frames respectively and the second ends of the compliant members are secured to the bulges of the frames respectively.
Further objectives and advantages of the present invention will become apparent from a careful reading of a detailed description provided hereinbelow, with appropriate reference to accompanying drawings.